Phase Transfer Catalyst - Dhrubajyoti Samanta This animation is about phase transfer catalysts and the way in which they can be used to improve the yields of certain reactions.

24/01/11 Master Layout

24/01/11 Instructions to animator: There are a total of 100 green dots and 100 yellow dots. 2. The green dots stay mostly in the white layer (only 3-5 go to the blue layer). 3. The yellow dots when not combined with the red dots stay mostly in the blue layer (only 3-5 dots go to the white layer). 4. A total of 50 red dots are added of which 40 combine with the yellow dots. 5. The red dots are initially evenly distributed number wise between the two layers. 6. When the red dots combine with yellow dots, initially all the combined dots stay in the blue layer. They slowly move to the white layer also and finally they are distributed evenly between the two layers.

Step 1: ActionDescription of ActionAudio Narration Display the text in the blue box Display the text in the blue box one sentence at a time *Read the sentences in the box as they appear* Phase Transfer Catalysts are very important catalysts used in organic reactions involving inorganic reactants. They become essential because the organic reactants stay largely in the organic layer while the inorganic reactants stay mostly in the inorganic or aqueous layer. Hence, the yield of such reactions remains very low in the absence of a phase transfer catalyst. Phase Transfer Catalysts are usually alkylated ammonium compounds with a few long alkyl chains. These compounds are soluble in both the organic phase and the inorganic phase and can freely move from one phase to another. They also have a property of being able to exchange ions with the inorganic reactants. Hence they are able to transfer the ions needed for the reaction to the organic phase where they may react with the organic reactants. Hence they bring about a great increase in the yield of reactions of organic reactants with inorganic ones.

Step 2: ActionDescription of ActionAudio Narration Display the text and the picture The text in the blue box is displayed and then the animation in the blue box is shown. An example of a phase transfer catalyst is shown: An example of a phase transfer catalyst: (C16H33)(C2H5)3N+Cl-

Step 3: ActionDescription of ActionAudio Narration Display the text and the Picture The text is displayed first and then the picture is shown. An example of a reaction which is catalyzed by phase transfer catalysts is shown. We have an organic compound (1,3 propandiol) which reacts with an inorganic compound (sodium sulphide). The organic compound remains almost completely in the organic liquid (Di Chloro Methane) while the inorganic compound remains almost completely in the inorganic liquid (water) A sample reaction for Phase Transfer Catalyst:

Step 4: ActionDescription of ActionAudio Narration Display the text and the picture The text in the blue box is displayed followed by the picture. *The text in the blue box is read out* The Phase Transfer Catalyst (as shown in a previous figure) exchanges its chloride ions for the sulphide ions and is now able to transport the sulphide ions from the inorganic phase to the organic phase where it is needed for the reaction.

Step 5: ActionDescription of ActionAudio Narration Without Phase Transfer Catalyst The balls keep to their respective coloured layers (green balls to the white layer and yellow balls to the blue layer) with only 5% of the balls going to the other layer. The green organic reactant molecules keep to the white organic layer and the yellow inorganic reactant molecules keep to the blue aqueous layer. Only a small percentage of the molecules travel across the interface to the other layer giving a low yield.

Step 6: ActionDescription of ActionAudio Narration Input Wait for the user to press the button before adding the red dots Please press the Add Phase Transfer Catalyst button to add the phase transfer catalyst and see the effect of its addition.

Step 6: ActionDescription of ActionAudio Narration With Phase Transfer Catalyst The red dots are added to the two liquids and they spread out in equal numbers in the two liquids. Slowly the yellow dots start joining with the red dots. Then slowly the red- yellow combined dots spread out equally into the top layer also. The phase transfer catalyst is freely soluble in both the phases and spreads almost equally among the two phases. It also exchanges its chloride ions for the sulphide ions and is able to transport the sulphide ions to the organic layer to a much higher extent than the case without the catalyst.

Step 6: ActionDescription of ActionAudio Narration With Phase Transfer Catalyst About 80% of the yellow dots attached to the red dots slowly change colour to the crème colour shown above and slowly get equally distributed between the two colored layers. As the colour of the yellow dots change, the colour of an equal number of green dots also change slowly to the light green colour. The sulphide ions transported to the organic layer by the phase transfer catalyst is able to react with the organic reactant to give the product. The catalyst is also able to transport out the hydroxyl ions formed into the aqueous layer so that the reaction keeps going forward.

Step 6: ActionDescription of ActionAudio Narration ResultNarration of the result. Thus we see that the phase transfer catalyst is able to carry the sulphide ions into the organic phase to a great extent. These sulphide ions are able to take part in the reaction. Thus the addition of phase transfer catalysts increases the yield of the reaction greatly.

24/01/11 Phase Transfer Catalysts - Dhrubajyoti Samanta DISPLAY AREA TEXT AREA

24/01/11 Links for further reading Web Link : Book : Phase-transfer catalysis: fundamentals, applications, and industrial perspectives, 1st Edition, Charles M. Starks, Charles Leonard Liotta, Marc Halpern, Springer, 1994